1. Field of the Invention
The present invention relates to laminated panels in general and, more particularly, to a laminated panel having a surface layer with improved durability and chemical resistance and methods for manufacturing the same.
2. Background Information
Many of today's chemical-resistant laminates are characterized by high cost, poor performance, or both. Chemical resistance is typically defined in terms of standards promulgated by the Scientific Equipment and Furniture Association (SEFA), and in particular the standard referred to as SEFA 8.1 (www.sefalabs.com). The aforementioned standard is a chemical spot test wherein a laminate is exposed to one or more of 49 different chemical reagents individually applied to the surface of a laminate and left there for a predetermined period of time. At the end of the predetermined time period, the reagent is removed and the laminate is evaluated for changes caused by the reagent. The ability of the laminate to withstand chemical degradation is the measure of the laminate's chemical resistance.
Some laminates provide chemical resistance by utilizing a relatively thick resin overlayer. The thick resin overlayer can give the laminate an undesirable hazy appearance and can also significantly increase the cost of the laminate. Other laminates utilize a fluoropolymer barrier to increase the chemical resistance of the laminate. Fluoropolymer barriers provide desirable resistance against certain chemicals, but offer relatively little protection against certain solvents. Still other laminates use E-B cured foils to create chemical resistance. Many E-B foils are not suitable for high-pressure laminate applications, however, as they cannot handle the relatively high pressures utilized in the lamination process. To be suitable, the basis weight of the foil must be increased, along with the degree of cure and the amount of topcoat applied, which makes these foils more costly.
The ability of a laminate to resist abrasive wear is a highly desirable quality in a laminate. Abrasion-resistant laminates often utilize an overlayer that includes a high concentration of abrasion resistant particles. The abrasion resistant particles protect the overlayer and adjacent decor layer against undesirable wear within the decor layer. Unfortunately, the abrasion resistant particles that help protect the laminate against abrasion also wear the machinery used in the laminate manufacturing process. Laminates are often formed between the press plates of a batch press under elevated temperature and pressure. The abrasion resistant particles within the outermost layer (e.g., an overlayer) wear the very expensive press plates, thereby shortening their useful life and increasing the overall cost of the process. Wear is particularly a problem for textured press plates. The “peaks and valleys” of the textured press plates create uneven loading, further accelerating wear of the “peaks” and other sharp features of the press plates.
In addition to wear and chemical resistance, an overlayer should have desirable clarity; e.g., a lack of undesirable tint or haziness (lack of clarity referred to hereinafter as “haziness”). Haziness can be caused by a variety of things, including impurities and/or the size of particles added to the resin formulation. Resin formulations often include additives (e.g., thickening agents, suspension agents, dispersants, etc.) to improve processing and physical qualities. Additives in solid particle form having a particle size of approximately two-hundred and fifty nanometers (250 nm) can cause haziness because of their size relative to the wavelength range of visible light.
What is needed, therefore, is a laminated panel and a method for making the same, having a desirable level of chemical resistance and durability for a given period of time, one that possesses desirable clarity, and one that is cost-effective.